The present invention relates to tridimensional shaped foam implements and methods of making such implements. More particularly, the present invention relates to tridimensional absorbent components useful in absorbent articles such as sanitary napkins, panty liners, tampons, and the like and methods of making such shaped absorbent components.
Absorbent articles such as sanitary napkins, pantiliners, and incontinence pads are devices that are typically worn in the crotch region of an undergarment. These devices are designed to absorb and retain liquid and other discharges from the human body and to prevent body and clothing soiling. Sanitary napkins are a type of absorbent article worn by women in a pair of panties that is normally positioned between the wearer""s legs, adjacent to the perineum. Sanitary napkins of a wide variety of shapes and dimensions are currently used by women for the collection of menses and other bodily discharges.
In the past, a number of efforts have been directed at providing sanitary napkins that maintain contact with the wearer""s body. One attempt to provide such body contact is disclosed in U.S. Pat. No. 2,747,575 issued May 29, 1956 to Mercer. The Mercer patent discloses a catamenial bandage having a longitudinal hump which bulges towards and may contact the body of the wearer. The catamenial bandage described in the Mercer patent suffers from several disadvantages, however. For instance, the size and shape of the absorbent pad and hump in the Mercer bandage appear to limit the conditions under which the bandage is able to maintain contact with (and conform to) the body of the wearer. The portions of the bandage that lie laterally to the sides of the hump are not thin and flexible. In addition, the hump of the Mercer bandage is made of a cellulosic material, and, as a result, may tend to collapse and become permanently distorted during use.
U.S. Pat. No. 4,425,130 issued to DesMarais on Jan. 10, 1984, discloses a compound sanitary napkin that comprises a primary menstrual pad and a panty protector joined to one another at their corresponding ends in such a manner that the two constituents are free to move relative to one another along essentially their entire common length. The primary menstrual pad is intended to absorb the bulk of the bodily fluids discharged by the user, while the panty protector is intended to protect the user""s garments from soiling. In use, the relative freedom of movement between the primary menstrual pad and the panty protector serves to maintain the primary menstrual pad adjacent the user""s crotch region while the panty protector remains associated with the user""s undergarment.
The current tendency has been to develop sanitary napkins that are increasingly thinner, and thus more comfortable and less obtrusive than prior sanitary napkins. Recently, efforts have been directed at developing thin sanitary napkins which have the capacity to absorb and contain medium to high menstrual discharges. Previously, such discharges could only be handled by relatively thick sanitary napkins. Examples of thin sanitary napkins having capacities great enough to handle medium to high menstrual flows are disclosed in U.S. Pat. Nos. 4,950,264 and 5,009,653, issued to Osborn, III, on Aug. 21, 1990 and Apr. 23, 1991, respectively.
It is also desirable that sanitary napkins, not only maintain contact with, but conform as closely as possible to the wearer""s body. Such a body-conforming capability increases the effectiveness of the sanitary napkin by reducing the possibility that menses will travel beyond the perimeter of the sanitary napkin and leak. There have been a number of recent efforts to provide sanitary napkins and other absorbent articles with improved body-conforming characteristics. In addition to serving as examples of thin sanitary napkins, the sanitary napkins disclosed in the above-mentioned Osborn patents also serve as examples of anatomically-conforming sanitary napkins. While the sanitary napkins disclosed in the Osborn patents work quite well, the search for improved sanitary napkins has continued.
For example, published PCT Application Serial No. WO 94/16658, published on Aug. 4, 1994, discloses a generally thin, flexible sanitary napkin which has a central absorbent hump, and is capable of handling medium to high menstrual flows. The hump is particularly useful in fitting into the space between the wearer""s labia to more readily intercept menses and other bodily discharges when they leave the wearer""s body. The search, however, has continued for Improved sanitary napkins, particularly sanitary napkins that will achieve even better fit within the space between the wearer""s labia majora, and which are more adept at absorbing blood-based liquids, such as menses.
Three dimensional absorbent articles designed for absorbing blood-based liquids are also known. Typically such articles are intended to enable intralabial interception of such fluids with extralabial storage of the absorbed fluids. One attempt to increase the body fitting capability of sanitary napkin has been to combine both a cupped and a humped shape in the same article, typically achieving a sanitary napkin having a flattened front portion combined with a raised rear portion, in order to better fit the variations in the anatomy in longitudinal direction. One such structure is described in U.S. Pat. No. 4,804,380, issued to Lassen, et al. on Feb. 14, 1989 which describes an article that has a substantially flat or concave front portion intended to cover area of the mons pubis, and a longitudinally oriented raised peak in the rear portion that is said to adjust and mold into the inverted-V shape of the rear portion of the labia. Although this type of structure does provide a sanitary napkin with a certain degree of three dimensionality, such structures still cannot actually fit the various complex body shapes of the female anatomy that comprise nonlinear grooves and nonplanar surfaces. The sanitary napkin of the ""380 reference is provided with its three dimensionality by mechanically shaping an initially flat structure. This means, for example, that the raised peak in the rear portion thereof has a rectilinear profile when seen in side view, and therefore it fails to conform properly to the corresponding non-linear profile of a wearer""s anatomy as seen in a longitudinal direction.
Another example of an absorbent article having three dimensionality is described in published PCT application Ser. No. WO 99/01095 (""095 application), published in the name of the Procter and Gamble Company on Jan. 14, 1999. The devices described therein have a profile along the longitudinal centerline that provides improved conformity to human female anatomical features allowing improved bodily fit. However, improvements are still needed because the complex set of fold lines and planar surfaces is difficult to fabricate. Further, the contours of the device are substantially linear and planar compared to the nonlinear nature of anatomical surfaces (See, for example, FIG. 4 thereof).
The development of highly absorbent articles for blood and blood-based liquids such as catamenial pads (e.g., sanitary napkins), tampons, wound dressings, bandages and surgical drapes can be challenging. Compared to water and urine, blood and blood based liquids such as menses are relatively complex mixtures of dissolved and undissolved components (e.g., erythrocytes or red blood cells). In particular, blood-based liquids such as menses are much more viscous than water and urine. This higher viscosity hampers the ability of conventional absorbent materials to efficiently and rapidly transport these blood-based liquids to regions remote from the point of initial discharge. Undissolved elements in these blood-based liquids can also potentially clog the capillaries of these absorbent materials. This makes the design of appropriate absorbent systems for blood-based liquids such as menses particularly difficult.
Foams of various types have been suggested for use in tampons, sanitary napkins and other articles that absorb blood and blood-based liquids. See for example U.S. Pat. No. 4,110,276 (DesMarais), issued Aug. 29, 1978 (soft, flexible, open celled foams made from polyurethanes, cellulose, or styrene/butadiene rubber that can be used in tampons and sanitary pads); U.S. Pat. No. 4,752,349 (Gebel), issued Jun. 21, 1988 (foams of xe2x80x9cmedium cell sizexe2x80x9d hydrophilized by surfactant treatment and having a density within the range of 0.1 to 0.8 g/cc); U.S. Pat. No. 4,613,543 (Dabi), issued Sep. 28, 1986 (hydrophilic cellular polymers used in catamenial products); U.S. Pat. No. 3,903,232 (Wood et al.), issued Sep. 2, 1975 (compressed hydrophilic polyurethane foams useful in biomedical applications, including catamenial devices); U.S. Pat. No. 4,049,592 (Marans et al.) issued Sep. 20, 1977 (biodegradable hydrophilic polyurethane foams highly absorptive upon contact with liquids or bodily liquids having utility in sanitary napkins and the like). Prior foams used in these products have tended to have relatively large cell sizes. As a result, these prior foams do not exert sufficient fluid capillary pressure for blood and blood-based liquids to acquire discharged menstrual liquids quickly from and through the topsheet of catamenial products such as sanitary napkins. This results in undesirable wetness since the surface in immediate contact with the body retains some of the fluid that is not absorbed into the core and is available to be transferred back onto the body of the wearer.
Suitable absorbent foams for absorbent products have also been made from a High Internal Phase Emulsion (hereafter referred to as a xe2x80x9cHIPExe2x80x9d). HIPE foams can provide the fluid capillary pressure necessary to remove most of the menstrual fluid from the body, or topsheet adjacent to the body, thus minimizing wetness. However, it has been found that the residual hydratable salts such as calcium chloride typically present in prior HIPE foams can impair the rapid acquisition blood and blood-based liquids by these foams, and especially the wicking of such liquids within these foams. As noted above, blood and blood-based liquids such as menses are more highly viscous than water and especially urine. The higher viscosity of these liquids is further increased by the presence of these salts. Moreover, prior HIPE foams often had a foam microstructure too small to admit readily the undissolved components of blood and blood-based liquids such as red blood cells.
Exemplary HIPE foam-based structures are described in, for example, U.S. Pat. No. 5,260,345 (DesMarais et al.), issued Nov. 9, 1993 and U.S. Pat. No. 5,268,224 (DesMarais et al), issued Dec. 7, 1993. These absorbent HIPE foams provide desirable urine handling properties, including: (a) relatively good wicking and fluid distribution characteristics to transport fluid away from the initial impingement zone and into the unused balance of the foam structure to allow for subsequent gushes of fluid to be accommodated; and (b) a relatively high storage capacity with a relatively high fluid capacity under load, i.e. under compressive forces. These HIPE absorbent foams are also sufficiently flexible and soft so as to provide a high degree of comfort to the wearer of the absorbent article; some of these foams, such as those described in U.S. Pat. No. 5,387,207 issued Feb. 7, 1995 (Dyer, et al.), can be made relatively thin until subsequently wetted by the absorbed body liquids. See also U.S. Pat. No. 5,147,345 (Young et al), issued Sep. 15, 1992 and U.S. Pat. No. 5,318,554 (Young et al), issued Jun. 7, 1994, which disclose absorbent cores having a fluid acquisition/distribution component that can be a hydrophilic, flexible, open-celled foam such as a melamine-formaldehyde foam (e.g., BASOTECT(trademark) made by BASF), and a fluid storage/redistribution component that is a HIPE-based absorbent foam.
The art has also considered the use of HIPE foams for absorption of blood and blood-based fluids. For example, U.S. Pat. No. 5,849,805, issued to Dyer on Dec. 15, 1998 describes a process for making HIPE foams capable of absorbing blood and blood-based fluids, especially menses. While this patent makes a passing mention of forming a HIPE into a single-piece catamenial pad, there is no description of how such pad formation may be done. In another example, U.S. Pat. No. 5,899,893, issued to Dyer, et al. on May 4, 1999 describes HIPE foam-containing absorbent articles that are particularly suited for absorption of blood and blood-based fluids. However, the absorbent articles described therein are all substantially planar and the HIPE foam is in a sheet form.
A HIPE foam-based absorbent article having tridimensional character is described in U.S. Pat. No. 5,873,869, issued to Hammons, et al. on Feb. 23, 1999 (""869 patent). The article described therein comprises a primary absorbent member in a tube form with a roughly triangular cross section and a secondary absorbent member. The primary absorbent member is assembled from a several sheets of a foam material derived from a HIPE and is sufficiently conformable to, at least partially, fit into a wearer""s interlabial space. The use of such HIPE foams in absorbent articles is discussed in greater detail below. While such structures provide desirable conformity, they are complex to assemble because they comprise many components requiring assembly into a functional article.
Other HIPE foams having three dimensionality are also known. For example, U.S. Pat. No. 3,256,219 (""219 patent), issued to Will on Jun. 14, 1966, describes coating a workpiece filling a mold with HIPE foams formulated from monomers such as styrene and styrene derivatives; acrylic and methacrylic acid esters, such as methyl methacrylate; and acrylonitriles. In particular, when using the HIPE in molds, the ""219 patent teaches blending the HIPE with a powder or viscous liquid polymer formed from the same monomer used in the HIPE. While such references may teach rudimentary aspects of producing tridimensional articles from HIPEs, there is no teaching of absorbent articles or of absorbent HIPEs. Further, and importantly, there is no teaching of suitable processes for forming three dimensional articles from the HIPEs disclosed therein, of suitable materials for use in a molding process, or of other information enabling one of skill in the art to produce a variety of molded articles that comprise a HIPE foam.
Therefore, it is desirable to provide an absorbent components for absorbent articles, such as sanitary napkins that maintain contact with and conform as closely as possible to the wearer""s body. It is further desirable to provide such components in a three dimensional configuration so as to facilitate such contact and conformity. It is still further desirable to produce such components from a foam material, such as a HIPE foam, which is especially suitable for handling, absorbing, and storing blood-based liquids, such as menses while being resilient so that the absorbent article can readily contact and conform to a wearer""s body. It is also desirable to produce such three dimensional absorbent foam components using a molding process so that three dimensional shapes matching the complex curvature of a wearer""s body can be provided.
It is further desirable to provide other tridimensional products from HIPE foams whereby the particular advantages of the foam composition can provide the article with properties that may be attainable only with difficulty if the article is produced from other materials and to produce such articles using molding processes amenable to high speed commercial production.
These and other aspects of the present invention will be more readily apparent when considered in reference to the following description and when taken in conjunction with the accompanying drawings.
The present invention is directed to a method of molding a foam material to produce three dimensional articles. Such three dimensional articles are particularly suitable for use as absorbent components in absorbent articles such as sanitary napkins, panty liners, interlabial devices, and adult incontinence pads to provide improved acquisition of blood-based liquids such as menses, and improved fit relative to a female wearer""s body. Other tridimensional foam based articles having particularly desirable combinations of foam properties and tridimensionality can also be produced using the method of the present invention.
The method of forming the molded foams used in the present invention allows these absorbent foams to have cells and holes small enough to provide a high capillary absorptive pressure but large enough to prevent or minimize blockage by the insoluble components of these liquids. In particular, the process of forming the molded foams comprises the steps of forming a HIPE wherein the HIPE is a water-in-oil emulsion wherein the oil phase comprises polymerizable monomers that are cured into a HIPE foam having the properties described below. The HIPE is deposited into a mold designed to hold the HIPE in the desired three dimensional configuration for use as an absorbent component while the HIPE cures into a HIPE foam. The molded HIPE foam is then removed from the mold and provided with any desired post molding treatment (e.g., washing and rehydrophilization). If desired, the molded article can be used as is or further converted into a finished article.
When the finished article is an absorbent article, the foam materials used for the absorbent article of the present invention are capable of absorbing blood and blood-based liquids such as menses and then moving these absorbed liquids efficiently to other regions of the foam. These absorbent polymeric foam materials comprise a hydrophilic, flexible, nonionic polymeric foam structure of interconnected open-cells. This foam structure has:
A) a capillary specific surface area in the range of from about 0.0060 to about 0.10 m2/cc;
B) a resistance to compression deflection of from about 5 to about 90% when measured under a confining pressure of 0.74 psi at 31xc2x0 C. after 15 minutes;
C) a free absorbent capacity of from about 15 to about 125 g/g;
D) less than about 2% of residual hydratable salts.
A particularly important attribute of the foams used in the present invention is that the connecting passages (holes) between the cells of these foams are sufficiently large to pass insoluble solids such as erythrocytes (mean diameter greater than about 8 xcexcm). As a result, these holes do not become blocked or obstructed by blood and blood-based liquids absorbed by the foam. Even though the cells and holes are large enough to allow free movement of insoluble components in blood and blood-based liquids, they are sufficiently small so as to produce the necessary high capillary absorption pressure required of absorbents used in catamenial products. In other words, these foams combine high capillary absorption pressure with sufficient openness to allow free movement of the insoluble components in blood and blood-based liquids such as menses. Typically, the cells of these foams have a number average cell size of from about 20 to about 2500 xcexcm, while the holes be tween these cells have a number average hole size of from about 5 xcexcm to about 60 xcexcm.